Cleaning method for a process of liquid immersion lithography

ABSTRACT

Problem: To provide a cleaning liquid and a cleaning method having excellent leaning capability. In a process of liquid immersion lithography, they can preventing the damage to be caused by the component released from the photoresist to photoexposure devices; the waste treatment is easy; the efficiency in substitution with the cleaning liquid for the medium for liquid immersion lithography is high, and the production cost is reduced not detracting from the throughput in semiconductor production. 
     Means for Solution: A cleaning liquid to be used for cleaning a photoexposure device in a process of liquid immersion lithography, which comprises at least 5% by mass of a nonionic surfactant containing at least one group selected from an ethyleneoxy group, a propyleneoxy group and a polyglycerin group, and a balance of water; and a cleaning method using it.

This is a continuation of Ser. No. 12/585,329 filed Sep. 11, 2009, nowabandoned, which is a continuation of Ser. No. 12/084,325 filed Apr. 30,2008, now abandoned, which is the National Stage of InternationalApplication No. PCT/JP2006/321477, filed Oct. 27, 2006.

TECHNICAL FIELD

The present invention relates to a cleaning liquid and to a cleaningmethod used for a process of liquid immersion lithography.

BACKGROUND ART

Photography is much used in fabrication of microstructures in variouselectronic devices such as semiconductor devices, liquid-crystaldevices. Recently, the increase in the technical level of large-scaleintegration and microfabrication is great, and it is desired to furtherimprove the technique of photoresist micropatterning inphotolithography.

At present, for example, photolithography in the forefront of the regionof high-technology has made it possible to form a photoresistmicropattern having a line width of 90 nm or so, and further studies anddevelopments are being made for micropatterning to a higher level to aline width of 65 nm or so.

For attaining micropatterning to such a higher level, in general, somemethods of improving photoexposure devices or photoresist materials maybe taken into consideration. Regarding the method of improvingphotoexposure devices, there may be mentioned a method of employingshort-wave light sources of F₂ excimer laser, EUV (extreme-ultravioletray), electron ray, X ray, soft-X ray, and a method of employing lenseshaving an increased numerical aperture (NA).

However, the method of employing such short-wave light sources requiresan additional expensive photoexposure unit. On the other hand, themethod of employing such increased-NA lenses is problematic in that,since the resolution and the focal depth range are in a trade-offrelationship, the increase in the resolution may lower the focal depthrange.

Recently, liquid immersion lithography has been reported as a techniqueof photolithography capable of solving these problems (for example, seeNon-Patent References 1 to 3). This method is for photoresist patterningthrough photoexposure of a photoresist film formed on a substrate, inwhich, in the photoexposure light pathway between the photoexposuredevice (lens) and the photoresist film, a liquid for liquid immersionlithography having a predetermined thickness is made to be on at leastthe photoresist film, and the photoresist film is exposed to light inthat condition to thereby form a photoresist pattern. In the method ofliquid immersion lithography, the photoexposure light pathway space,which is an inert gas such as air or nitrogen in conventional methods,is substituted with a liquid for liquid immersion lithography having alarger refractive index than that of the space (vapor) and having asmaller refractive index (n) than that of the photoresist film (forexample, pure water, fluorine-containing inert liquid), and theadvantage of the method is that, even though a photoexposure lightsource having the same wavelength level as that in conventional methodsis used therein, the method may attain a high-level resolution like thecase that uses a photoexposure light having a shorter wavelength or usesa high-NA lens and, in addition, the method does not result in thereduction in the focal depth range.

To that effect, the process of liquid immersion lithography is muchnoticed in the art, since it realizes photoresist patterning of highresolution to a good focal depth at low costs, using any lens actuallymounted on the existing photoexposure devices therein.

However, in the process of liquid immersion lithography, thephotoexposure is attained while a medium for liquid immersionlithography is made to be between the lens for photoexposure and thephotoresist film, and therefore the method is problematic in that thephotoexposure device may be damaged by the component released from thephotoresist film into the medium for liquid immersion lithography (forexample, the crystal material for the lens for photoexposure may befogged, and as triggered by it, the transmittance of the lens may belowered and the exposure may be uneven).

To solve the problem, employed are a method of improving the photoresistmaterial to thereby prevent it from releasing the constitutivecomponent, and a method of providing a layer of a protective film on thephotoresist layer to thereby prevent the photoresist from releasing theconstitutive component. However, the former method is limited in itsdevelopment in point of the photoresist material and has another problemin that it could be hardly applicable to a wide variety of photoresists;and even the latter method could not completely prevent the photoresistfrom releasing the constitutive component.

Given that situation, another method of solving the above-mentionedproblem has been proposed, still using the photoresist and theprotective film now widely used in the art. The method comprisescleaning the optical lens member of the photoexposure device that iskept in contact with the medium for liquid immersion lithography, usinga cleaning liquid (for example, see Patent Reference 1).

However, the cleaning liquid described in the patent publicationcomprises an organic, ketone-type or alcohol-type solvent; and when theorganic solvent is used in the cleaning liquid and when the cleaningliquid and water used as the medium for liquid immersion lithographyhave the same flow line, then the waste treatment is difficult; and inaddition, the cleaning liquid has another problem in that, when thecleaning liquid remaining between the lens and the photoresist layer isreplaced with a medium for liquid immersion lithography in a process ofphotoexposure, it requires a time-consuming additional step of dryingthe photoexposure device prior to the liquid replacement. Further, theeffect of the method of removing the component released fromphotoresist, which is a high-risk factor of contamination, isinsufficient, and the method could hardly keep the optical properties ofphotoexposure devices.

-   Non-Patent Reference 1: “Journal of Vacuum Science & Technology B”,    USA, 1999, Vol. 17, No. 6, pp. 3306-3309-   Non-Patent Reference 2: “Journal of Vacuum Science & Technology B”,    USA, 2001, Vol. 19, No. 6, pp. 2353-2356-   Non-Patent Reference 3: “Proceedings of SPIE”, USA, 2002, Vol. 4691,    pp. 459-465-   Patent Reference 1: JP-2005-157259A

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

The present invention has been made in consideration of theabove-mentioned situation, and its object is to provide a cleaningliquid having excellent cleaning capability and applicable to a processof liquid immersion lithography that uses photoresist and protectivefilm now widely used in the art. The cleaning liquid is effective forreducing the damage of photoexposure devices caused by the componentsreleased from photoresist, its waste treatment is easy, and itssubstitution with a medium for liquid immersion lithography is easy, andit contributes toward production cost reduction not detracting from thethroughput in semiconductor production.

Means for Solving the Problems

For solving the above-mentioned problems, the invention provides acleaning liquid to be used for cleaning a photoexposure device in aprocess of liquid immersion lithography, which comprises at least 5% bymass of a nonionic surfactant containing at least one group selectedfrom an ethyleneoxy group, a propyleneoxy group and a polyglyceringroup, and a balance of water.

The invention also provides the above cleaning liquid that furthercontains an organic solvent in an amount of less than 50% by mass.

The invention also provides a cleaning method in a process of liquidimmersion lithography that comprises using a photoexposure deviceprovided with at least an optical lens member, a wafer stage, aliquid-introducing flow line and a liquid-discharging flow line,introducing a medium for liquid immersion lithography into the spacebetween the optical lens member and the object for photoexposure mountedon the wafer stage, through the liquid-introducing flow line, then thusfilling the space with the medium for liquid immersion lithography andsimultaneously discharging the medium for liquid immersion lithographythrough the liquid-discharging flow line to attain photoexposure; thecleaning method comprises introducing, after photoexposure, theabove-mentioned cleaning liquid through the same introducing flow lineas that used for the introduction of the medium for liquid immersionlithography and making the cleaning liquid in contact with the opticallens member for a predetermined period of time so as to clean theoptical lens member, and discharging the used cleaning liquid throughthe same discharging flow line as that used for the discharging of themedium for liquid immersion lithography.

The invention also provides a cleaning method in a process of liquidimmersion lithography that comprises filling the space between theoptical lens member of a photoexposure device and an object forphotoexposure mounted on the wafer stage, with a medium for liquidimmersion lithography; the cleaning method comprises, afterphotoexposure, spraying the above-mentioned cleaning liquid on theoptical lens member, or wiping the optical lens member with a clothsprayed with the cleaning liquid, thereby to clean the optical lensmember.

Advantages of the Invention

According to the invention, there are provided a cleaning liquid havingexcellent cleaning capability and a cleaning method using it. Thecleaning liquid has high cleaning capability, not causing damage to thecrystal material for lenses for photoexposure; and its waste treatmentis easy; its substitution with a medium for liquid immersion lithographyis easy; and it contributes toward production cost reduction notdetracting from the throughput in semiconductor production.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention is described in detail hereinunder.

The cleaning liquid of the invention contains at least 5% by mass of anonionic surfactant having at least one group selected from anethyleneoxy group, a propyleneoxy group and a polyglycerin group, andwater.

The nonionic surfactant is preferably at least one selected from alkylethers and/or esters having from 5 to 25 carbon atoms, fatty acid ethersand/or esters, sorbitan acid ethers and/or esters, and acetylene glycolethers and/or esters, having at least one group selected from anethyleneoxy group, a propyleneoxy group and a polyglycerin group.

Above all, preferred for use herein are polyoxyethylene (hereinafterthis may be referred to as “POE”) alkyl ethers, POE sorbitan acidesters, POE fatty acid esters, POE acetylene glycol ethers.

POE alkyl ethers include POE lauryl ether, POE oleyl ether, POE stearylether, POE behenyl ether, POE octyldodecyl ether, POE cholestanol ether.

POE fatty acid esters include POE monooleate, POE distearate, POEmonooleate.

The amount of the nonionic surfactant is at least 5% by mass in thecleaning liquid of the invention, preferably from 5 to 30% by mass, morepreferably from 7 to 25% by mass. The amount falling within the definedrange brings about the advantages that the cleaning liquid reduces thedamage to the photoexposure devices by the component released fromphotoresist, the waste treatment is easy, the efficiency in substitutionwith the cleaning liquid for the medium for liquid immersion lithographyis high, the production cost is reduced not detracting from thethroughput in semiconductor production, and the cleaning liquid hasexcellent cleaning capability.

The cleaning liquid of the invention contains water as the balance.Water is preferably pure water, deionized water or the like.

The cleaning liquid of the invention may further contain an organicsolvent. The organic solvent is preferably at least one selected fromalkanolamines, alkylamines, polyalkylene-polyamines, glycols, ethers,ketones, acetates, and carboxylates.

The alkanolamines include monoethanolamine, diethanolamine,triethanolamine, 2-(2-aminoethoxy)ethanol (=diglycolamine),N,N-dimethylethanolamine, N,N-diethylethanolamine,N,N-dibutylethanolamine, N-methylethanolamine, N-ethylethanolamine,N-butylethanolamine, N-methyldiethanolamine, monoisopropanolamine,diisopropanolamine, triisopropanolamine. However, the invention shouldnot be limited to these examples.

The alkylamines include 2-ethyl-hexylamine, dioctylamine, tributylamine,tripropylamine, triallylamine, heptylamine, cyclohexylamine. However,the invention should not be limited to these examples.

The polyalkylene-polyamines include diethylenetriamine,triethylenetetramine, propylenediamine, N,N-diethylethylenediamine,N,N′-diethylethylenediamine, 1,4-butanediamine, N-ethyl-ethylenediamine,1,2-propanediamine, 1,3-propanediamine, 1,6-hexanediamine. However, theinvention should not be limited to these examples.

The glycols include ethylene glycol, diethylene glycol, propyleneglycol, glycerin, 1,2-butylene glycol, 1,3-butylene glycol, 2,3-butyleneglycol. However, the invention should not be limited to these examples.

The ethers include ethylene glycol monomethyl ether (=methylcellosolve), ethylene glycol monoethyl ether (=ethyl cellosolve),ethylene glycol diethyl ether, ethylene glycol diisopropyl ether,ethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether,propylene glycol monoethyl ether, diethylene glycol monomethyl ether,diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether(=butyldiglycol), diethylene glycol dimethyl ether, diethylene glycoldiethyl ether, dipropylene glycol monomethyl ether, benzyl ethyl ether,dihexyl ether. However, the invention should not be limited to theseexamples.

The ketones include acetone, methyl ethyl ketone, diethyl ketone, methylpropyl ketone, methyl isobutyl ketone, methyl amyl ketone, diisopropylketone, cyclobutanone, cyclopentanone, cyclohexanone. However, theinvention should not be limited to these examples.

The acetates include ethylene glycol monomethyl ether acetate (=methylcellosolve acetate), ethylene glycol monoethyl ether acetate (ethylcellosolve acetate), ethylene glycol mono-n-butyl ether acetate(=n-butyl cellosolve acetate), propylene glycol monomethyl etheracetate. However, the invention should not be limited to these examples.

The carboxylates include, for example, alkyl- or aliphatic-carboxylates,and monohydroxycarboxylates; concretely including methyl lactate, ethyllactate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate,amyl acetate, isoamyl acetate. However, the invention should not belimited to these examples.

In the invention, alkanolamines, glycols, ethers, ketones, acetates andcarboxylates are preferred for the above organic solvent.

In case where an organic solvent is added to the cleaning liquid of theinvention, its content is preferably less than 50% by mass, morepreferably from 1% by mass to less than 50% by mass, even morepreferably from 3 to 30% by mass. The content falling within the definedrange brings about the advantages that the cleaning liquid reduces thedamage to the photoexposure devices by the component released fromphotoresist, the waste treatment is easy, the efficiency in substitutionwith the cleaning liquid for the medium for liquid immersion lithographyis high, the production cost is reduced not detracting from thethroughput in semiconductor production, and the cleaning liquid hasexcellent cleaning capability.

The cleaning method with the cleaning liquid of the invention is, forexample, as follows:

First, an ordinary photoresist composition is applied on a substratesuch as silicon wafer as an object for photoexposure, using a spinner,and then prebaked (PAB treatment) to form a photoresist film thereon. Asthe case may be, after one layer of an organic or inorganicantireflection film (underlayer antireflection film) is formed on thesubstrate, the photoresist film may be formed thereon.

Not specifically defined, the photoresist composition may be anyphotoresist developable with an aqueous alkali solution, includingnegative and positive photoresists. The photoresist includes (i) apositive photoresist that contains a naphthoquinonediazide compound anda novolak resin, (ii) a positive photoresist that contains a compoundcapable of generating an acid through exposure to light, a compoundcapable of decomposing with an acid to have an increased solubility inaqueous alkali solution, and an alkali-soluble resin, (iii) a positivephotoresist that contains a compound capable of generating an acidthrough exposure to light, and an alkali-soluble resin having a groupcapable of decomposing with an acid to have an increased solubility inaqueous alkali solution, and (iv) a negative photoresist that contains acompound capable of generating an acid or a radical by light, acrosslinking agent and an alkali-soluble resin. However, the inventionshould not be limited to these.

As the case may be, a protective film may be formed on the surface ofthe photoresist film.

Next, the substrate with the photoresist film formed thereon is mountedon a wafer stage of a photoexposure device. Preferably, thephotoexposure device comprises, in addition to the wafer stage, anoptical lens member disposed above the wafer stage to face it, as spacedfrom it by a predetermined distance therebetween, and additionallycomprises a liquid introducing flow line and a liquid discharging flowline.

Next, a medium for liquid immersion lithography is introduced into thespace between the photoresist film-having substrate and the optical lensmember in one direction to the wafer stage through the liquidintroducing flow line, and at the same time with it, the medium forliquid immersion lithography is discharged (drawn) out in the otherdirection from the wafer stage through the liquid discharging flow line,and in that condition while the space is filled with the medium forliquid immersion lithography, the photoresist film is selectivelyexposed to light through a mask pattern.

In a process of local liquid immersion lithography, while thephotoexposure lens is scanned at high speed and while a medium forliquid immersion lithography is continuously dropwise applied onto thephotoresist film through a liquid introducing nozzle (liquid introducingflow line), the photoresist film is selectively exposed to light. Thephotoresist film on the substrate, onto which a medium for liquidimmersion lithography is continuously dropwise applied, is selectivelyexposed to light through a mask pattern. The excessive medium for liquidimmersion lithography is discharged out through the liquid dischargingnozzle (liquid discharging flow line).

Apart from the above, also employable is a method of exposing thephotoresist layer-having substrate to light, while the substrate is keptimmersed in a medium for liquid immersion lithography.

Under any condition as above, at least the space between the lens andthe photoresist layer-having substrate is filled with a medium forliquid immersion lithography.

In that condition, the photoresist film on the substrate is selectivelyexposed to light through a mask pattern. Accordingly, in this stage, thephotoexposure light reaches the photoresist film after having passed viathe medium for liquid immersion lithography.

In this stage, the photoresist-constituting component may be releasedfrom the photoresist film and may dissolve in the medium for liquidimmersion lithography, and it may adhere to the photoexposure device asa contaminant thereto.

The photoexposure light is not specifically defined, for which usableare any radiations such as ArF excimer laser, KrF excimer laser, F₂excimer laser, EB, EUV, VUV (vacuum ultraviolet ray).

Not specifically defined, the medium for liquid immersion lithographymay be any liquid having a refractive index larger than that of air andsmaller than that of the photoresist film used (object forphotoexposure). In the invention, preferably used is a liquid having arefractive index of at least 1.44 that is smaller than the refractiveindex of the photoresist film used as so mentioned in the above, forimproving the resolution. The medium for liquid immersion lithography ofthe type includes water (pure water, deionized water; refractive index1.44), liquids containing various additives added thereto for increasingthe refractive index, fluorine-containing inert liquids, silicon-basedinert liquids, hydrocarbon liquids. In addition, also usable herein is amedium for liquid immersion lithography having high-refractivitycharacteristics, which may be developed in near future. Specificexamples of the fluorine-containing inert liquids are liquidscomprising, as the principal ingredient thereof, a fluorine-containingcompound such as C₃HCl₂F₅, C₄F₉OCH₃, C₄F₉OC₂H₅, C₅H₃F₇. Of those,preferred is water (pure water, deionized water) in a case of using aphotoexposure light having a wavelength of 193 nm (e.g., ArF excimerlaser), from the viewpoint of the cost, the safety, the environmentalproblem and the wide-range applicability thereof. However, when aphotoexposure light having a wavelength of 157 nm (e.g., F₂ excimerlaser) is used, then preferred for it is a fluorine-containing solventfrom the viewpoint that the absorption of the photoexposure light by thesolvent is small.

After the step of photoexposure in liquid immersion as above, thesubstrate is taken out of the medium for liquid immersion lithography,and then the liquid is removed from the substrate.

Next, the cleaning liquid of the invention is brought into contact withthe site that was contacted with the medium for liquid immersionlithography in the photoexposure device, especially the optical lensmember, whereby the component released from the photoresist film isremoved and cleaned off. Not specifically defined, the contact time maywell be a period of time within which the photoresist-released componentcould be removed and cleaned off; and in general, it may be from 30seconds to 10 minutes or so. Accordingly, even though a componentreleased from a photoresist film has adhered to the photoexposuredevice, especially to the optical lens member, it may be immediatelyremoved, and therefore, the invention secures high-definitionphotoexposure treatment all the time in a cleaned condition. Through thephotoexposure, a photoresist pattern of high reliability can be formed.

The cleaning liquid of the invention is so constituted that it containsan organic solvent and water in a predetermined ratio, and therefore, itmay be used through the same flow lines as those used in introductionand discharging of the medium for liquid immersion lithography.Accordingly, the cleaning liquid does not require any additional flowlines for it, therefore contributing to production cost reduction.

For bringing the cleaning liquid into contact with the optical lensmember, any other method than the above may also be employed. Forexample, the cleaning liquid of the invention may be directly sprayed onthe optical lens member, or the optical lens member may be wiped with acloth sprayed with the cleaning liquid, whereby the optical lens membermay be cleaned.

The cleaning method is not limited to those exemplified in the above.

Next, the exposed photoresist film is subjected to PEB (post exposurebaking), and then developed with an alkali developer comprising anaqueous alkali solution. The alkali developer may be any ordinary one.As a result of the alkali development treatment, the protective film isdissolved and removed along with the soluble part of the photoresistfilm. After the development, the substrate may be post-baked.Subsequently, this is rinsed with pure water or the like. The rinsingwith water may be effected, for example, as follows: While the substrateis rotated, water is dropped or sprayed onto the surface of thesubstrate so that the developer and the protective film component andthe photoresist composition having been dissolved by the developer arewashed away. Then, this is dried, and the photoresist film is patternedin accordance with the profile of the mask pattern, thereby giving aphotoresist pattern.

In that manner, a photoresist pattern is formed. Thus formed, thephotoresist pattern has a microstructure of good resolution, and inparticular it may be a line-and-space pattern having a small pitch.

EXAMPLES

The invention is described in more detail with reference to thefollowing Examples, to which, however, the invention should not belimited.

Examples 1 to 6 Comparative Examples 1 to 4

A test tool of the following constitution was prepared for reproducingthe contamination of a photoexposure lens in a condition of liquidimmersion lithography.

First, a photoacid generator in a photoresist component, “TPS-PFBS(tetraphenylsulfonium perfluorobutanesulfonate)”, which is expected tobe a cause of contamination of photoexposure lens, was dissolved in purewater, and the aqueous 500-ppm solution was used as a test chemicalliquid.

Next, a transparent cell was disposed in the course of a duct structure,in which a liquid could flow at a constant flow rate, and the above testchemical liquid was introduced into the duct from its one end, whiledischarged out through the other side. A photoexposure lens for liquidimmersion lithography was disposed on either one side of the transparentcell through which the duct was not disposed.

In the direction to the side of the cell on which the photoexposure lensfor liquid immersion lithography was disposed, a pulse-wave ArF excimerlaser was applied, and in that condition, the test liquid chemical wasled to flow through the transparent cell with the photoexposure lens forliquid immersion lithography disposed therein.

The ArF excimer laser was pulsewise radiated as above, and this isbecause both the contamination caused by the photoacid generator asdissociated and ionized through irradiation with light and that causedby the photoacid generator not dissociated through no irradiation withlight could be reflected as the contamination of the test tool to be thecontamination in actual photoexposure.

Using the test tool of the constitution as above, the above-mentionedtest chemical liquid was led to flow through it at a flow rate of 0.1L/min, and with that, an ArF excimer laser was applied to it at anexposure level of 0.18 mJ at a pulse of 1.76×10⁵, whereby the surface ofthe photoexposure lens was made to adsorb a contaminant.

The photoexposure lens for liquid immersion lithography with thecontaminant adhering thereto was dipped in a cleaning liquid having thecomposition shown in Table 1 for 10 minutes, then subsequently rinsedwith water for 30 seconds, and dried by nitrogen blowing; and then thiswas visually checked, and the cleaning effect for it was evaluatedaccording to the following evaluation standards. The results are shownin Table 1.

[Evaluation Standards for Cleaning Effect]

◯: Contaminant completely removed.

Δ: Contaminant remained but only slightly.

X: Contaminant remained.

TABLE 1 Cleaning Composition of Cleaning Liquid (mas. %) Effect Example1 POE lauryl ether (10) + water (90) ◯ Example 2 POE sorbitan acid ester(10) + water ◯ (90) Example 3 POE lauryl acid ester (10) + water (90) ◯Example 4 POE acetylene glycol ether (10) + water ◯ (90) Example 5 POElauryl ether (10) + water (85) + ◯ PGME (5) Example 6 POE sorbitan acidester (10) + water ◯ (85) + BDG (5) Comparative BDG (100) Δ Example 1Comparative water (100) X Example 2 Comparative water (99.8) + ATOH(0.2) X Example 3 Comparative water (99.8) + POE lauryl ether (0.2) XExample 4

In Table 1, the abbreviations mean the following compounds.

PGME: propylene glycol monomethyl ether,

BDG: diethylene glycol mono-n-butyl ether (=dibutyl diglycol),

ATOH: acetylene alcohol-base surfactant.

As is obvious from the results in Table 1, it is known that the cleaningliquid of the invention has excellent cleaning capability.

INDUSTRIAL APPLICABILITY

The cleaning liquid and the cleaning method of the invention haveexcellent leaning capability, and in a process of liquid immersionlithography in which a photoresist and a protective film now widely usedin the art are used, they can prevent the damage to be caused by thecomponent released from the photoresist to photoexposure devices. Inaddition, the waste treatment is easy, the efficiency in substitutionwith the cleaning liquid for the medium for liquid immersion lithographyis high, and the production cost is reduced not detracting from thethroughput in semiconductor production.

The invention claimed is:
 1. A cleaning method in a process of liquidimmersion lithography that comprises using a photoexposure deviceprovided with at least an optical lens member, a wafer stage, aliquid-introducing flow line and a liquid-discharging flow line,introducing a medium for liquid immersion lithography into a spacebetween the optical lens member and an object for photoexposure mountedon the wafer stage, through the liquid-introducing flow line, then thusfilling the space with the medium for liquid immersion lithography andsimultaneously discharging the medium for liquid immersion lithographythrough the liquid-discharging flow line to attain photoexposure; afterphotoexposure, introducing a cleaning liquid through the sameintroducing flow line as that used for the introduction of the mediumfor liquid immersion lithography and contacting the cleaning liquid withthe optical lens member for a predetermined period of time so as toclean the optical lens member, and discharging the used cleaning liquidthrough the same discharging flow line as that used for the dischargingof the medium for liquid immersion lithography, wherein the cleaningliquid comprises 7 to 25% by mass of polyoxyethylene lauryl ether, and abalance of water.
 2. The cleaning method of claim 1, wherein cleaning ofthe photoexposure device is to clean a site of the photoexposure devicethat was kept in contact with the medium for liquid immersionlithography during photoexposure.
 3. The cleaning method of claim 2,wherein the site of the photoexposure device that was kept in contactwith the medium for liquid immersion lithography during photoexposure isthe optical lens member.
 4. The cleaning method of claim 1, whichfurther contains an organic solvent in an amount of less than 50% bymass.
 5. The cleaning method of claim 4, wherein the organic solvent isat least one selected from alkanolamines, alkylamines,polyalkylene-polyamides, glycols, ethers, ketones, acetates andcarboxylates.
 6. A cleaning method in a process of liquid immersionlithography that comprises filling a space between an optical lensmember of a photoexposure device and an object for photoexposure mountedon a wafer stage, with a medium for liquid immersion lithography toattain photoexposure; after photoexposure, spraying a cleaning liquid onthe optical lens member, or wiping the optical lens member with a clothsprayed with the cleaning liquid, thereby to clean the optical lensmember, wherein the cleaning liquid comprises 7 to 25% by mass ofpolyoxyethylene lauryl ether, and a balance of water.